1. Field of the Invention
The invention relates to a press roller with interchangeable external sleeve, whose internal sleeve, holding the external sleeve, is provided with boreholes, which can be loaded with pressurized air, in order to facilitate the pulling on and off of the external sleeve.
In printing machines the sleeves, provided with the printing plates or blocks, must be substituted in accordance with the different printing, jobs for the purpose of converting to the modified printing jobs. Furthermore, it can become necessary to interchange the sleeves of ink or anilox rollers. To interchange the sleeves it is necessary to provide auxiliary devices to expand the sleeves in the circumferential direction, because they sit with a press fit that is friction tight on the roller or an intermediate pipe.
2. Description of the Related Art
A prior art device for pulling block-bearing sleeves on and off a roller of a printing machine is explained with reference to FIG. 2 of the drawings.
FIG. 2 depicts a press roller 1, for example a form cylinder, onto whose internal sleeve 2 can be pulled an external sleeve (not illustrated), which bears, for example, blocks. To guarantee that the external sleeve sits with a press fit on the internal sleeve, the said external sleeve must be expanded in the circumferential direction when pulled on and off, in order to make the exchange even possible. The external sleeve is slid on the internal sleeve 2 in the direction of arrow A. To make the sliding on and pulling off process easy, the interior of the press roller 1 is provided with an inner cylinder 3, whose left side exhibits a central shaft journal 4, which is held in an axial borehole 5 of the left front disk 6, which is connected to the left shaft journal 7 of the press roller. On the right side the inner roller sleeve 2 is mounted by means of an annular recess on a disk 8, which is also connected to a shaft journal 9. The inside of the disk 8 exhibits a recess, which forms a circular disk 10, on which the sleeve of the inner cylinder 3 is mounted.
The right end of the sleeve 2 of the press roller is provided with boreholes 11, which are spaced apart over a circumferential line and which empty into a ring groove 12, which is recessed into the circumference of the disk 8. Furthermore, the sleeve 2 is provided with radial boreholes 13, which empty into the ring chamber 14 between the inner cylinder 3 and the sleeve 2.
The right shaft journal 9 is provided with an axial borehole 15, which extends into the front disk 8. The front disk 8 exhibits the axial borehole 15, from which extends the radial borehole 16, which empties into the ring groove 12. Furthermore, the radial borehole 16 runs eccentricly to the central line of the press roller through a borehole 17, which runs in the axial direction and empties into the ring chamber 14.
Compressed air is fed through the axial borehole 15 to the press roller for the purpose of sliding the external sleeve on and off. But to generate the requisite compressed air in the radial boreholes 11 and 13, the ring chamber 14 must be completely filled with compressed air. However, the ring chamber 14 is relatively voluminous so that it also forms a buffer for the fed-in compressed air and needs large quantities of compressed air in order to generate in the boreholes 11, 13 the pressure needed to expand the sleeve to be slid on and to form a cushion of compressed air, on which the expanded external sleeve can be slid on and pulled off.
Therefore, the object of the invention is to provide a press roller of the type described in the introductory part that has no buffer space impeding the pressure buildup so that the fed-in compressed air is directly and immediately available to expand the external sleeve to be slid on or to be pulled off and that generates a compressed air cushion, which improves the sliding properties.
The invention solves this problem with a press roller of the type described in the introductory part in that the boreholes are connected to compressed air lines, which are led through the interior of the internal sleeve.
In the press roller of the invention the radial boreholes of the internal sleeve are directly connected to the lines, introducing the compressed air, so that there is no dead space that has to be filled with compressed air, before the boreholes are loaded with air of the requisite pressure. Thus, to pull a sleeve on or off, one need only load the line, leading to the compressed air lines, with compressed air in order to feed the radial boreholes with compressed air.
A preferred embodiment provides that a shaft journal of the press roller is provided with an axial borehole, which is connected to the pipes, feeding the compressed air. To feed the boreholes with compressed air, the axial borehole is connected to a compressed air source.
It is expedient that the compressed air lines comprise pipes that are connected to the compressed air connection.